Structural characterization and, where feasible, chemical synthesis of the high affinity microbial iron carriers, generically termed siderophores, will be performed in order to expand the list of candidate compounds for iron chelate therapy. A systematic chemical synthesis of citrate-hydroxamate type siderophores, such as aerobactin, awaitin and arthrobactin will be completed in order to assess the promise of such substances for the treatment of the transfusion induced siderosis resulting from the supportive therapy for Cooley's, Sickle Cell and aplastic anemias. The kinetics and equilibria for iron removal from saturated iron transferrin by both newly isolated and synthetic siderophores will be determined. Because of ease of preparation, superior iron complexing activity and anticipated low toxicity in animal systems, special efforts will be centered upon compounds containing the 2,3-dihydroxybenzoyl nucleus.